Isomerization of alkyl benzenes using a nu-1 zeolite catalyst

ABSTRACT

A process for the isomerization of xylenes using the hydrogen form of new zeolite &#34;nu-1&#34; having a silica to alumina ratio of 20 to 150 and a characteristic X-ray diffraction pattern and adsorption properties.

This is a division, of application Ser. No. 727,773 filed Sept. 29,1976, now U.S. Pat. No. 4,060,590.

The present invention relates to a zeolite-like material hereinafterreferred to as zeolite ν - 1, that is, nu-1, to a method of making itand to processes using it as a catalyst.

Zeolite nu-1 can be made from a synthesis mixture containing a silicasource, an alumina source and a methylated quaternary ammonium compoundand/or cationic degradation product thereof and/or mixtures, for exampleof trimethylamine and methanol, that produce a methylated quaternaryammonium compound; alternatively the corresponding phosphonium compoundscan be used.

A considerable number of zeolite preparations involving thetetramethylammonium cation has already been described. These aresurveyed in "Zeolite Molecular Sieves" by D. W. Breck (Wiley -Interscience 1974), pages 304 - 312, 348 - 378. The following is a listof what are believed to be the most pertinent examples, with references:

    ______________________________________                                        N-A, N-X, N-Y                                                                              US 3306922                                                       ZK-4         UK 1062879                                                       alpha        UK 1074130                                                       omega        UK 1178186                                                       TMA-O, TMA-E Journal of the Chemical Society                                               (London) 1970A, 1470-1475                                        N            US 3414602                                                       ZSM-4        UK patents 1117568, 1227294,                                                  1297256, 1321460 and 1365318                                     TMA-offretite                                                                              UK 1188043                                                       ______________________________________                                    

Zeolite nu-1 is, however, shown by X-ray and other characterisinginformation to be different from these and all other synthetic andnatural zeolites. The X-ray data are presented hereinafter as a recorderchart (Example 13), a table of intensities derived from a recorder chart(Example 1), a table of intensities derived directly from diffractionmeasurements (Examples 8, 13, and 14) or the report of a comparison witha standard nu-1 chart. The data were determined using copper K alpharadiation.

We believe that the distinctive structure and properties of nu-1 resultfrom exploration of synthesis at higher temperatures and higher watercontents than have previously been used, with high silica to aluminaratios.

The invention provides zeolite nu-1 having a composition in the range

    0.9 to 1.3 R.sub.2 O . Al.sub.2 O.sub.3 . 20 to 150 SiO.sub.2 . 0 to 40 H.sub.2 O

where R is one or more of hydrogen, ammonium, phosphonium or 1/n of acation of a metal of valency n and having an X-ray diffraction patternwhen R is H substantially as shown in Table 1.

This definition includes both freshly prepared zeolite nu-1 ("freshlyprepared" means the product of synthesis and washing, with optionaldrying) and also forms of it resulting from dehydration and/orcalcination and/or ion exchange. In freshly prepared nu-1 R is orincludes ammonium or phosphonium selected from methylated quaternaryammonium and methylated quaternary phosphonium and cationic degradationproducts thereof (referred to hereinafter as Q) and may include analkali metal, especially sodium. The freshly-prepared material may alsocontain quaternary compound trapped in the zeolite structure, but thisdoes not constitute part of the composition for the purposes of thedefinition. The proportion of such compound is typically 0.5 to 2.5 molsof Q₂ O per Al₂ O₃.

The silica to alumina ratio is preferably at least 40.

                  TABLE 1                                                         ______________________________________                                        Zeolite nu-1 in hydrogen form                                                 d (A)     100 I/Io    d (A)       100 I/Io                                    ______________________________________                                        8.87      18          3.965       73                                          8.28      69          3.845       74                                          6.53      43          3.81        22                                          6.19      75          3.687       16                                          4.43      52          3.508       29                                          4.30      51          3.256       27                                          4.08      37          2.858       15                                          4.03      100                                                                 ______________________________________                                    

The H₂ O content of freshly prepared nu-1 depends on the conditions inwhich it has been dried after synthesis.

In calcined forms of nu-1, R may be alkali metal but includes less or noammonium or phosphonium compound, since these are burnt out in thepresence of air, leaving hydrogen as the balancing cation.

Among the ion-exchanged forms of nu-1 the ammonium (NH₄ ⁺) is ofimportance since it can be readily converted to the hydrogen form bycalcination. The hydrogen-form and forms containing metals introduced byion exchange are described further below.

The data shown in Table 1 include estimated measurement errors andrepresent ranges of variation such as are common in the zeolite art asthe result of impurities, of changes in the associated cationsrepresented by R, and variations in detailed crystal structure withinthe scope of the essential nu-1 structure. In particular, the d-spacingsin Table 1 may be up to 4% larger or 2% smaller, the zeolite may containa combination of nu-1 forms from various parts of the d-spacing range,and in certain forms the 6.5 - 6.6 A line may be split into two. Theaccompanying drawing refers to the high d-spacing type with the splitpeak.

It will be noticed that the data in Table 1, which relates to thepreparation described in Example 8, differ from those quoted in theprovisional specifications filed on 3 October 1975 and 9 February 1976in not including certain lines. Of these lines, that at d (A) 19.4 hassince been identified with the impurity kenyaite and those at 6.17 and3.19 as sodalite.

Zeolite nu-1 is characterised further by the following dye absorptionproperties:

    ______________________________________                                        (a)   cationic dyes                                                                 acriflavine  nil                                                              phenosafranine                                                                             nil                                                              carbocyanine very strong, purple or purple/blue                               methyl red   very strong                                                      toluylene red                                                                              nil                                                        (b)   other dyes                                                                    alizarin     weak                                                             aurin        nil                                                              aluminon     nil without TMA                                            ______________________________________                                    

The determination of these properties in comparison with other zeolitesis described in Example 21 below.

Zeolite nu-1 is yet further characterised by its adsorption capacity formolecules of various sizes. The following % w/w adsorptive capacities atp/po = 0.5 were observed for the hydrogen nu-1 of Example 8, which isbelieved to be typical:

                  TABLE 2                                                         ______________________________________                                        water 25° C                                                                              6.8                                                         n - hexane 25° C                                                                         2.7                                                         isobutane 25° C                                                                          0.9                                                         p - xylene 25° C                                                                         nil in 2 hours                                                                1.9 in 24 hours                                             ______________________________________                                    

The slow adsorption of p - xylene suggest that nu-1 has internal spaceslarge enough to accommodate the p - xylene molecule, but that theentranceports to such spaces are small, probably about 6.0 A.

From Table 2 it is evident that zeolite nu-1 absorbs water to a greaterextent than n- hexane by a factor of 1.5 to 4.0, based on weightpercentages. Zeolite nu-1 is therefore to be considered as fallingwithin the class of so-called "hydrophilic" zeolites, even though itssilica to alumina ratio can be over 30 and thus at a level previouslydisclosed to be characterised by hydrophobic behaviour, that is,absorbing more n - hexane than water.

Whereas other characterising properties of nu-1 may yet be found, it ischaracterised particularly by its catalytic properties, in the hydrogenform, of high activity for xylenes isomerization and ethylbenzeneconversion, with selectivity against xylenes disproportionation.

The invention provides also a method of making zeolite nu-1 by reactingan aqueous mixture comprising at least one silica source, at least onealumina source and at least one methylated quaternary ammonium ormethylated quaternary phosphonium compound, the mixture having the molarcomposition

SiO₂ /Al₂ O₃ -- at least 10, preferably 20 to 200, especially 40 to 100

Na₂ O/SiO₂ -- 0 to 0.4, especially 0.05 to 0.25

(Na₂ O + Q₂ O)/SiO₂ -- 0.1 to 6.0, preferably 0.1 to 5.0, especially 0.2to 0.3

H₂ o/(na₂ O + Q₂ O) -- 5 to 500, especially 100 to 200

Q₂ o/(na₂ O + Q₂ O) -- 0.05 to 1.0, especially 0.4 to 0.7

where Q is methylated quaternary ammonium or methylated quaternaryphosphonium Na₂ O and Q₂ O refer to free Na₂ O and Q₂ O only. Theexpressions "free Na₂ O" and "free Q₂ O" are generally understood in thezeolite art to denote hydroxides or salts of very weak acids such asaluminic or silicic acid such that such Na₂ O and Q₂ O are effective inthe zeolite synthesis reaction. If waterglass is used as a silicasource, the content of free Na₂ O and/or Q₂ O can be decreased to withinthe specified range by adding acid or adding alumina and/or Q in theform of a salt of a strong acid, for example as sulphate, nitrate orhalide.

The silica source can be any of those commonly considered for use insynthesising zeolites, for example powdered solid silica, silicic acid,colloidal silica or dissolved silica. Among the powdered silicas usableare precipitated silicas, especially those made by precipitation from analkali metal silicate solution, such as the type known as "KS 300" madeby AKZO, and similar products, aerosil silicas, fume silicas and silicagels suitably in grades for use as reinforcing pigments for rubber orsilicone rubber. Colloidal silicas of various particle sizes may beused, for example 10 - 15 or 40 - 50 microns, as sold under theRegistered Trade Marks "LUDOX", "NALCOAG" and "SYTON". The usabledissolved silicas include commercially available waterglass silicatescontaining 0.5 to 6.0, especially 2.0 to 4.0 mols of SiO₂ per mol ofalkali metal oxide, "active" alkali metal silicates as defined in UKPat. No. 1,193,254, and silicates made by dissolving silica in alkalimetal or quaternary mixture.

The alumina source is most conveniently sodium aluminate, but can be orinclude an aluminium an aluminium salt for example the chloride, nitrateor sulphate or alumina itself, which should preferably be in a hydratedor hydratable form such as colloidal alumina, pseudobohmite, bohmite,gamma alumina or the alpha or beta trihydrate.

In the reaction mixture for synthesising nu-1 at least part of thealumina can be provided in the form of one or more aluminosilicates.

The aluminosilicate compound provides preferably at least 20%,especially 50 - 100% of the alumina source. If the aluminosilicatecompound contains sufficient silica, it can provide the whole of thesilica source. However, since the silica to alumina ratio of zeolitenu-1 is much higher than that of readily available aluminosilicatecompounds, the reaction mixture will normally contain a further silicasource.

The aluminosilicate compound can be synthetic or naturally-occurring. Ifit is synthetic it can for example be a crystalline compound, such as azeolite or an amorphous compound such as a gel or a zeolite precursor ora silica/alumina cracking catalyst. If it is naturally-occurring it maybe for example a clay such as kaolin (especially in the form known asmetakaolin made by calcination of kaolin at 500° - 950° C, especially530° - 600° C), or one or more of attapulgite, dickite, halloysite,illite or montmorillonite. A naturally-occurring zeolite may be used ifdesired. Substances such as nepheline and kalsilite, which are availablenaturally or synthetically, can be used. In assembling the reactionmixture, account should be taken of other reactants introduced as partof the aluminosilicate material, such as water and alkali metalcompounds; and preferably any interfering constituents such as compoundsof Group II elements should be substantially absent. The aluminosilicatecompound used can be one that has been made by treating with acid orwith non-interfering cations the corresponding compound containinginterfering cations. If desired, the aluminosilicate can have beende-aluminised by acid or chromium bleaching.

The use of aluminosilicate starting material makes possible a variant ofthe method in which such a material is introduced in shaped particulateform (especially as approximately spherical granules 1 - 10 mm indiameter of cylindrical compressed pellets or extrusions 2 - 10 mm indiameter and 5 - 20 mm in length) and the silica content, temperatureand time are chosen so as to effect conversion to zeolite nu-1 only inthe outer portions of those particles. By this method zeolite nu-1 canbe obtained directly in shaped particles and the agglomerationprocedures necessary for making such particles from powder areunnecessary. Typical conditions for such a variant of the method include

SiO₂ / Al₂ O₃ -- 12 - 25

temperature -- 150° - 200° C

time -- 1.5 to 3.0 days

The water content of the reaction mixture is preferably over 500,especially in the range 1000 to 4000 mols per mol of Al₂ O₃.

The relative proportions of Q₂ O and Na₂ O can be chosen in relation tothe intended sodium content of the zeolite produced, the sodium contentand thus the need for ion-exchange being lower, the lower the proportionof Na₂ O. The preferred range 0.4 to 0.7 is of general usefulness ingiving a zeolite requiring a moderately intense ion exchange treatment,yet without the high cost of a high proportion of Q₂ O.

The reaction should be continued preferably until the time when thezeolite product contains at least 50% w/w of nu-l. This time depends onthe temperature and relative concentrations of reactants and on thewhether the reaction mixture is quiescent or agitated. If the time ofreaction is excessive, then zeolite nu-1 is converted into otherproducts. The reaction is followed preferably by sampling the mixtureand examining it at intervals. A typical reaction time is in the range12 to 300 hours. The temperature is suitably in the range 80° - 300° C,preferably 135° - 280° and especially in the range 150° - 250° C.

In addition to the ingredients already mentioned, the reaction mixturecan contain seed zeolite and/or a mineralising agent such as a nitrate,halide or sulphate of an alkali metal. Such an agent may be added assuch or formed in situ by the reaction of an alkali metal hydroxide,aluminate or silicate with the appropriate acid or quaternary oraluminium salt.

At the end of the reaction, the solid phase is collected on a filter andwashed and is then ready for further steps such as drying, dehydrationand ion-exchange.

If the product of the reaction contains alkali metal ions, these have tobe at least partly removed in order to prepare the hydrogen form ofnu-1, and this can be done by ion exchange with an acid, especially astrong mineral acid such as hydrochloric acid or by way of the ammoniumcompound, made by ion exchange with a solution of an ammonium salt suchas ammonium chloride. Such ion exchange can be carried out by slurryingonce or several times with the solution. The zeolite is usually calcinedafter ion exchange and may be calcined before or between stages.

In general, the cation(s) of zeolite nu-1 can be replaced by anycation(s) of metals, and particularly by those in

Groups IA, IB, IIA, IIB, III (including rare earths), VIIA (includingmanganese), VIII (including noble metals) and by lead and bismuth. (ThePeriodic Table is as in "Abridgments of Specifications" published by theUK Patent Office).

In order to prepare a catalyst zeolite nu-1 can be incorporated in aninorganic matrix, with other materials which can be either inert orcatalytically active. The matrix may be present simply as a bindingagent to hold the small zeolite particles (0.005 to 10 microns)together, or it may be added as a diluent to control the amount ofconversion in a process which may otherwise proceed at too high a rate,leading to catalyst fouling as a result of excessive coke formation.Typical inorganic diluents include catalyst support materials such asalumina, silica and kaolinic clays, bentonites, montmorillonites,sepiolite, attapulgite, Fullers earth, synthetic porous materials suchas SiO₂ Al₂ O₃, SiO₂ -ZrO₂, SiO₂ -ThO₂, SiO₂ -BeO, SiO₂ -TiO₂, or anycombination of these oxides. An effective way of mixing zeolite nu-1with such diluents is to mix appropriate aqueous slurries in a mixingnozzle and then to spray-dry the slurry. Other ways of mixing can beused.

If zeolite nu-1 in any cationic form or as a catalytic composite isexchanged or impregnated with hydrogenation/dehydrogenation components,such as Ni, Co, Pt, Pd, Re, Rh, hydrocracking and reforming catalystscan be made, especially if the Na₂ O content is less than 0.03% w/w.

A preferred hydrocarbon conversion process according to this inventioncomprises contacting a feed of an alkylbenzene or a mixture ofalkylbenzenes under isomerisation conditions in the vapour or liquidphase with a catalyst comprising zeolite nu-1, especially in thepreferred hydrogen form with a sodium oxide content of less than 0.15%w/w.

In the vapour phase, suitable isomerisation conditions include atemperature in the range 100° to 600° C, preferably 200° to 450° C and apressure in the range 0.5 to 50, preferably 1 to 5, atmospheres absolute(ata).

In the liquid phase, suitable isomerisation conditions include atemperature in the range 0° to 350° C, a pressure in the range 1 to 200,preferably 5 to 70 ata and, in a flow system, a space velocity in therange 1 to 100, preferably 1 to 30 w/w hour, the higher flow rates beingused at the higher temperatures. Optionally a diluent is present,suitably one or more of those having a critical temperature higher thanthe isomerisation temperature being used and including toluene,ethylbenzene, trimethylbenzene, naphthenes and paraffins. Preferably,the diluent if present, amounts to 1 to 90% by weight of the feed to theisomerisation reaction. In the above-mentioned processes the catalystpreferably contains no hydrogenation/dehydrogenation component.

Optionally the isomerisation reaction is conducted in the presence ofhydrogen. A suitable mole ratio of hydrogen to alkylbenzene lies in therange 3 to 30:1. If hydrogen is used, it is preferred that the catalystshould comprise a metal of Group VIII of the Periodic Table togetherwith the zeolite. Preferably the metal of Group VIII is platinum. Theamount of metal used preferably lies in the range 0.1 to 2% by weight ofmetal based on the total weight of catalyst. If desired, the catalystmay contain one or more additional metals, for example rhenium, suitablyin the range 0.1 to 2% by weight based on the total weight of catalyst.

Preferably the alkylbenzene is a xylene, for example m-xylene forconversion to p-xylene, or a mixture of xylenes, possibly withethylbenzene. The amount of ethylbenzene present will depend to someextent on the source of the xylenes mixture but will usually lie in therange 0 to 25% by weight of the feedstock. In certain prior art xylenesisomerisation processes it is necessary to limit the amount ofethylbenzene in the feedstock to a relatively small amount, say lessthan 6% as above this level, the catalysts used cannot break down theethylbenzene, which therefore tends to build up in recycle streams. Theprocess of the invention is able to handle feedstocks containingrelatively high (e.g. 6 - 25%) as well as relatively low amounts ofethylbenzene.

The isomerisation may be carried out in the presence of water vapour ina concentration of, for example 500 to 10,000 and preferably 1000 to5000 parts per million by weight of the feedstock.

In the following Examples the ingredients had the following properties:

Silica AKZO KS 300 98.9% SiO₂ -- 1.1% Na₂ O

Sodium aluminate formula 1.25 Na₂ O . Al₂ O₃

"tmaoh" represents tetramethylammonium hydroxide and the solution usedcontained 25% w/w of TMAOH. metakaolin formula Al₂ O₃ . 2 SiO₂ ;prepared by calcining kaolin in air for 17 hours at 550° C.

EXAMPLE 1 Preparation of Na - Q form of zeolite nu-1

For this preparation the synthesis mixture had the composition Al₂ O₃ .59.3 SiO₂ . 12.65 Na₂ O . 10.76 Q⁺ . 36.06 OH⁻⁻ . 3580.3 H₂ O. Solidsilica (36 g of AKZO grade KS 300) was suspended in a mixture of 39.2 gof TMAOH solution and 500 g water. Next 1.8 g solid sodium aluminate and8.6 g solid sodium hydroxide were dissolved in 115 g water and stirredinto the silica suspension (10 minutes). The resulting slurry was heatedfor 8 days at 170° C in a 1 liter Pyrex (R.T.M.) liner in a 5 literautoclave without agitation. After cooling to about 60° C, the slurrywas filtered and washed with 500 mls hot water, and dried at 120° C. Theproduct, zeolite nu-1, had the X-ray diffraction data shown in Table 3and the composition 0.7 Na₂ O . 0.3 Q₂ O . Al₂ O₃ . SiO₂ . 6 H₂ O whereQ is tetramethyl ammonium, and a crystallite size of about 5 microns.

This product was calcined in air overnight at 550° C and was found tohave substantially the same X-ray diffraction pattern as the hydratedtetramethylammonium-containing zeolite nu-1.

                  TABLE 3                                                         ______________________________________                                        X-ray diffraction data = freshly prepared nu-1 (Example 1)                    d(A)         100 I/Io   d(A)      100 I/Io                                    ______________________________________                                        K     19.4       2.5        4.01    100                                              11.33     2.5        3.95    38                                              8.80       8.0        3.83    62                                              8.23       41         3.51    35                                              6.94       2.5        3.42    24                                              6.49       32         3.24    11                                        S-1   6.17       55         S 3.19  11                                              5.61       11         3.08    11                                              5.34       10         2.98    11                                              4.41       46         2.94    5                                               4.28       49         2.85    8                                                                     2.76    8                                                                     2.73    4                                                                     2.67    10                                        ______________________________________                                         Notes:                                                                        K denotes a line identified as Kenyaite                                       S denotes lines identified as sodalite                                        S-1 denotes a nu-1 line reinforced by a neighboring sodalite line        

EXAMPLE 2 Preparation of hydrogen form of nu-1

The calcined product of Example 1 was slurry-exchanged three times withits own weight of 10% ammonium chloride solution at 25° C for 1 hour foreach exchange stage. The product was calcined in air overnight at 550°C, and was found to have substantially the same X-ray diffractionpattern as the zeolite nu-1 originally made in Example 1, a crystallitesize of about 5 μ, and the composition:

    0.01 Na.sub.2 O . Al.sub.2 O.sub.3 . 55 SiO.sub.2

this hydrogen nu-1 zeolite had a water adsorptive capacity of 3.5% w/w(p/po = 0.7, 25° C), and adsorbed 3% w/w n hexane (p/po = 0.6 25° C). Itdid not significantly adsorb p-xylene. These results suggest a windowsize of at least 5A, but less than 6A.

EXAMPLE 3 Isomerisation of xylenes

The hydrogen zeolite nu-1 of Example 2 was employed as a catalyst in theisomerisation of xylene mixtures containing only 7% p-xylene and 11%ethylbenzene. It was found that the catalyst exhibited very low decayrates, and gave virtually complete and very advantageous conversion ofethylbenzene to diethylbenzene; it also gave very low xylene loss. Thep-xylene lift to equilibrium levels on zeolite nu-1 was obtained at atemperature 200° C lower than on SiO₂ /Al₂ O₃ xylene isomerisationcatalyst.

EXAMPLE 4 Preparation using mixture of lower sodium content

0.9 g sodium aluminate powder and 2.2 g sodium hydroxide pellets weredissolved in 300 ml water. 29.4 g of TMAOH solution were added to thissolution and 18 g fine silica stirred into it. The resulting suspensionwas stirred for 1 hour at 60° C and then maintained at 170° C in anautoclave for 61/2 days. The reaction mixture thus had a compositionwith molar ratios as follows:

SiO₂ /Al₂ O₃ = 60; Na₂ O/SiO₂ = 0.11; (Na₂ O + Q₂ O)/SiO₂ = 0.25; H₂O/(Na₂ O + Q₂ O) = 230; Q₂ O/(Na₂ O + Q₂ O) = 0.57 where Q istetramethylammonium. The mixture after cooling to room temperature wasfiltered, washed with water, and dried in air at 120°. The resultingfinely divided solid was slurry-exchanged by suspension in a solution of20 g ammonium chloride in 300 ml water at 50° for 0.5 hour. The zeoliteformed was filtered off and washed with water. At this stage the sodiumcontent of the zeolite was 0.14% Na, by weight. The material was thencalcined at 500° C for 16 hours. Three further treatments with theammonium chloride solution reduced the sodium content to 0.08% Na.

EXAMPLE 5 Xylenes isomerisation

Pellets consisting of 67% zeolite in the hydrogen form prepared asdescribed in Example 4 and 33% pseudobohmite alumina (25% water) wereprepared. 7 g of pellets were placed in a laboratory-size reactor forxylenes isomerisation. A feed of mixed xylenes (composition as shown inTable 4) was passed over the catalyst at flows varying from 10cc to 15ccper hour. Three runs totalling 24 hours each were made at 450° C andduring each run the catalyst showed no loss of activity. At the end ofeach run, examination of the catalyst revealed only very slight evidenceof carbon lay-down on the catalyst. The feed composition and productcomposition in the three runs are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                                Composition                                                                   of       Composition of Product                                               Feed (Wt%)                                                                             Run 1     Run 2   Run 3                                      ______________________________________                                        Benzene   0.05       0.90      0.71  0.69                                     Toluene   0.27       0.74      0.58  0.60                                     Ethylbenzene                                                                            5.80       4.53      4.64  4.77                                     Paraxylene                                                                              8.38       18.92     17.94 17.57                                    Metaxylene                                                                              54.77      47.94     48.47 48.65                                    Orthoxylene                                                                             29.30      25.94     26.43 26.54                                    Aromatic C.sub.9 's                                                                     0.3        --        0.53  --                                       Aromatic C.sub.10 's                                                                    0.05       --        0.05  --                                       n-C.sub.9 paraffin                                                                      1.20       undeterm'd                                                                              0.75  undeterm'd                               ______________________________________                                    

The xylenes loss by disproportionation in each run was about 0.7%, basedon the toluene formed. In conventional isomerisation processes usingsilica/alumina catalysts, a loss of about 2% usually occurs and theactivity of such catalysts usually declines in similar experiments.

EXAMPLE 6

The process described in Example 5 was repeated using the same catalystand under the same conditions except that the feed contained arelatively large amount of ethyl benzene. The feed composition andproduct composition in 2 runs are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                                Composition of                                                                          Composition of Product                                              Feed (wt%)                                                                              Run 1      Run 2                                            ______________________________________                                        Benzene   --          1.31       1.42                                         Toluene   0.27        0.59       0.60                                         n-nonane  1.35        1.09       1.16                                         Ethylbenzene                                                                            12.20       9.46       9.42                                         Para-xylene                                                                             7.58        16.52      16.47                                        Meta-xylene                                                                             51.27       46.18      46.07                                        Ortho-xylene                                                                            27.34       24.18      24.86                                        Aromatic C.sub.9                                                                        0.34                                                                Aromatic C.sub.10                                                                       0.05                                                                ______________________________________                                    

This example shows that the catalyst comprising nu-1 zeolite is able tohandle a feedstock containing a relatively large amount of ethylbenzene,the latter being cracked to form benzene.

The activity and selectivity of the hydrogen form of zeolite nu-1 ofExample 4 were better than those of the sample prepared in Example 2.The reasons for this are not altogether clear but it is believed thatamong the factors playing a part may be the following:

(a) the smaller crystallite size of the Example 4 zeolite, most of thecrystallites being less than 1 μ in size.

(b) the relatively low sodium content of the Example 4 zeolite.

(c) the modified method of preparation; (i) whereas in Examples 1 and 2the zeolite was washed, dried at 120°, calcined at 550° C,slurry-exchanged with ammonium chloride solution and then againcalcined, in Example 4 calcination was carried out only after theslurry-exchange with ammonium chloride; and (ii) in the reaction mixturea rather higher ratio Q₂ O/Na₂ O was used than in Example 1.

EXAMPLE 7

Example 1 was repeated subject to the modification that the synthesiswas carried out under 20 ata pressure of nitrogen and without agitation,so as to ensure quiescent conditions. The product had the composition

    0.7 Na.sub.2 O . 2.3 Q.sub.2 O . Al.sub.2 O.sub.3 . 52 SiO.sub.2 . 10.5 H.sub.2 O

of which about 2.0 molecules of Q₂ O are non-structural and acrystallite size of 3 to 5 microns. Its X-ray diffraction pattern wastypical of zeolite nu-1.

EXAMPLE 8 Preparation of hydrogen form of nu-1

The product of Example 7 (1.3% w/w Na₂ O) was mixed with 2 ml of 5% w/whydrochloric acid per gram of product. The mixture was boiled underreflux for 5 hours, then filtered and washed with demineralised water.The washed product (0.3% w/w Na₂ O) was re-slurried with 60 ml of 0.365%w/w hydrochloric acid per gram of solid, held at 50° C for 1 hour, thenfiltered, washed with demineralised water and dried. The dried productcontained 0.019% w/w Na₂ O. It was then calcined at 450° C overnight toeffect controlled burn-off of its content of tetramethylammonium withoutexcessive temperature rise. The calcined product had the composition

    0.01 Na.sub.2 O . Al.sub.2 O.sub.3 . 50 SiO.sub.2

its % w/w adsorption capacity for water and n-hexane was measured at 25°C, p/po 0.5, with the following results:

water -- 6.8

isobutane -- 0.9

n-hexane -- 2.7

p xylene -- nil after 2 hours, 1.9 after 24 hours

These adsorption data suggest that ports into the zeolite structure areof diameter not over 6.0 A.

The X-ray diffraction data for this hydrogen nu-1 are set out in Table6.

When tested as in Examples 5 and 6, this zeolite sample was more activeand selective than that of Example 4.

                                      TABLE 6                                     __________________________________________________________________________    d (A)   Est. error                                                                          100 I/Io                                                                             d (A)                                                                              Est. error                                                                          100 I/Io                                                                              d (A)   Est. error                                                                           100                    __________________________________________________________________________                                                           I/Io                   11.45   0.04  4      3.76 0.01  ˜4                                                                              2.612   0.005  3    b                 8.87    0.03  18     3.687                                                                              0.005 16      2.574   0.005  1    s                 8.28    0.02  69     3.645                                                                              0.004 13 s    2.523   0.005  ˜1               6.53    0.02  43     3.508                                                                              0.004 29 b    2.503   0.004  4                      6.31    0.03  ˜11 s                                                                          3.430                                                                              0.005 8       2.488   0.004  5                      6.19    0.02  75     3.387                                                                              0.008 ˜1                                                                              2.471   0.003  6                      5.74    0.02  3      3.256                                                                              0.004 27 b    2.448   0.003  ˜1               5.63    0.02  11 b   3.15 0.01  2 s     2.436   0.003  4                      5.36    0.01  10     3.087                                                                              0.005 13 b    2.40    0.01   1    b                 4.61    0.01  10     2.998                                                                              0.004 11 b    2.345   0.003  2                      4.43    0.01  52     2.948                                                                              0.006 7       2.325   0.005  4    b                 4.30    0.01  51     2.912                                                                              0.004 10      2.300   0.002  5                      4.15    0.02  ˜2                                                                             2.876                                                                              0.005 11      2.253   0.002  1                      4.08    0.02  ˜37                                                                            2.858                                                                              0.004 15                                            4.03    0.01  100    2.823                                                                              0.004 7                                             3.965   0.005 73     2.773                                                                              0.005 10 b                                          3.94    0.01  shoulder                                                                             2.748                                                                              0.003 12 b                                          3.845   0.005 74     2.671                                                                              0.004 10 b                                          3.81    0.01  ˜22                                                                            2.630                                                                              0.003 2                                             __________________________________________________________________________    ˜                                                                         = approximately                                                             s = lines due to sodalite type impurity                                       b = broad line                                                                  = incompletely resolved lines                                           

EXAMPLE 9 Preparation on a larger scale

Example 7 was repeated with the modification that the scale was on thebasis of 46.4 g of the sodium aluminate (0.26 mol of Al₂ O₃) and thatsynthesis was carried out at 180° C for 3 days in a "Pyrex"(R.T.M.)-lined 25 liter autoclave. The product was found by X-raydiffraction to be very similar to that of Example 7. Its composition,after drying at 120° C, was

    0.06 Na.sub.2 O . 2.2 Q.sub.2 O . Al.sub.2 O.sub.3 . 49.9 SiO.sub.2 . 8.9 H.sub.2 O

of the 2.2 Q₂ O about 1.1 molecules are loosely bound, leaving 1.1molecules forming part of the zeolite structure.

EXAMPLE 10 Preparation using more concentrated synthesis mixtures

Example 1 was repeated using 25% less water and with a synthesis time of6 days at 180° C, in a 5 liter "Pyrex" (R.T.M.)-lined autoclave withoutagitation and without gas under pressure. The product after drying at120° C had the composition

    0.34 Na.sub.2 O . 1.9 Q.sub.2 O . Al.sub.2 O.sub.3 . 40 SiO.sub.2 . 9.2 H.sub.2 O

of which 1.1 molecules of Q₂ O are non-structural. Its X-ray diffractionpattern was of the low d-spacing type similar to the product of Example7.

EXAMPLE 11 Preparation at lower sodium content and higher concentration

A mixture having the composition

    1.89 Na.sub.2 O . 13.75 Q.sub.2 O . Al.sub.2 O.sub.3 . 59.3 SiO.sub.2 . 1930 H.sub.2 O

was reacted on the scale of 3.3 g of sodium aluminate (0.018 mol Al₂ O₃)was reacted quiescently in a "Pyrex" (R.T.M.)-lined 5 liter autoclaveunder 80 ata nitrogen pressure at 170° C for 8 days. The solid phase wascollected on a filter, washed, dried at 120° C, and then had thecomposition

    0.11 Na.sub.2 O . 1.6 Q.sub.2 O . Al.sub.2 O.sub.3 . 66 SiO.sub.2 . 7 H.sub.2 O

of which 0.6 molecule of Q₂ O is non-structural.

Its X-ray diffraction pattern differed from that of Table 1 in havingdoubled main peaks, suggesting that it consisted of a mixture of low dand high d material.

EXAMPLE 12

Example was repeated subject to the modifications that the synthesis wascarried out in a 1 liter stainless steel autoclave with stirring at 500rpm. Samples were taken at intervals and examined by X-ray diffraction.From 17 hours to 89 hours reaction time, at which the synthesis wasvoluntarily stopped, the solid phase contained zeolite nu-1 as its solecrystalline constituent. Its X-ray diffraction pattern was substantiallythe same as that of Example 11, except the peak at 6.6 A was split.

EXAMPLE 13 Synthesis mixtures of very low sodium content

(a) A reaction mixture of composition

    0.64 Na.sub.2 O . 5.4 Q.sub.2 O . Al.sub.2 O.sub.3 . 59.3 SiO.sub.2 . 1059 H.sub.2 O

was prepared using as alumina source 6.2 g of pseudobohmite containing200 ppm of Na₂ O and introducing it by dissolving it in TMAOH solutionat 60° for 1 hour. It was then reacted in a 1 liter stainless steelautoclave at 180° C for 24 hours with agitation. The product afterwashing and drying at 120° C overnight had the composition

    0.09 Na.sub.2 O . 2.9 Q.sub.2 O . Al.sub.2 O.sub.3 . 47.8 SiO.sub.2 . 4.1 H.sub.2 O

of which 1.9 molecules of Q₂ O are non-structural.

Its X-ray diffraction pattern was as shown in Table 7 and theaccompanying drawing. The d spacings are about 1% higher than in Table 1and two peaks occur at 6.5-6.6 A.

(b) A reaction mixture of composition

    0.008 Na.sub.2 O . 5.4 Q.sub.2 O . Al.sub.2 O.sub.3 . 60 SiO.sub.2 . 945 H.sub.2 O

was prepared as in (a), but using ingredients selected to introducestill less sodium. After a synthesis time of 48 hours but otherwise inthe condition of (a) the product had the composition and X-raydiffraction pattern similar to (a).

It is thus possible to produce zeolite nu-1 directly in a substantiallysodium-free form, convertible to the hydrogen form without ion exchange.

                                      TABLE 7                                     __________________________________________________________________________    d (A) Est. error                                                                          100 I/Io                                                                            d (A)                                                                              Est. error                                                                          100 I/Io                                                                           d (A)  Est error                                                                           100 I/Io                       __________________________________________________________________________    11.56 0.06  2     3.906                                                                              0.005 86     2.893                                                                              0.003 7                              8.97  0.03  26    3.842                                                                              0.005 34     2.794                                                                              0.003 14                             8.33  0.02  62    3.819                                                                              0.008 ˜9                                                                             2.766                                                                              0.003 17                             6.60  0.02  27    3.713                                                                              0.004 21     2.710                                                                              0.003 10                             6.54  0.02  27    3.562                                                                              0.004 43     2.693                                                                              0.003 4                              6.26  0.02  72    3.468                                                                              0.007 ˜1                                                                             2.635                                                                              0.002 4                              5.86  0.03  1     3.441                                                                              0.004 6      2.552                                                                              0.005 1                              5.765 0.02  3     3.305                                                                              0.004 17     2.532                                                                              0.002 3                              5.675 0.02  9     3.261                                                                              0.004 22     2.506                                                                              0.002 5                              5.65  0.02  9     3.209                                                                              0.006 1      2.487                                                                              0.002 7                              5.39  0.01  11    3.147                                                                              0.004 ˜5                                                                             2.449                                                                              0.002 5                              4.642 0.007 11    3.125                                                                              0.003 21     2.421                                                                              0.004 ˜1                       4.476 0.007 67    3.064                                                                              0.005 3      2.408                                                                              0.004 2                              4.324 0.006 62    3.021                                                                              0.004 8      2.349                                                                              0.004 3                              4.161 0.008 ˜6                                                                            3.007                                                                              0.004 8      2.339                                                                              0.004 5                              4.101 0.006 47    2.981                                                                              0.003 10     2.321                                                                              0.002 8                              4.047 0.007 100   2.949                                                                              0.003 11     2.304                                                                              0.004 1                              4.010 0.005 37    2.897                                                                              0.006 ˜5                                                                             2.285                                                                              0.002 2                              3.969 0.005 47    2.881                                                                              0.004 19     2.269                                                                              0.002 1                              __________________________________________________________________________    ˜                                                                         = approximately                                                               = incompletely resolved lines                                           

EXAMPLE 14

A reaction mixture similar to that of Example 1 and having thecomposition

    11.7 Na.sub.2 O . 5.2 Q.sub.2 O . Al.sub.2 O.sub.3 . 60.5 SiO.sub.2 . 37.83 H.sub.2 O

was reacted quiescently for 1 day at 230° C under autogenous pressure.The solid phase, after washing and drying contained alpha-quartz asimpurity and a nu-1 component having inter alia the following lines inits X-ray diffraction pattern:

                  TABLE 8                                                         ______________________________________                                        d A                  100 I/Io                                                 ______________________________________                                        8.98                 17                                                       8.39                 55                                                       6.60                 39                                                       6.27                 57                                                       4.48                 53                                                       4.34                 48                                                       4.13                 41                                                       4.07                 100                                                      4.01                 62                                                       3.995                                                                         3.896                74                                                       3.555                26                                                       3.294                32                                                       ______________________________________                                    

Comparison with the patterns for Examples 1 and 8 shows that this is anexample of the high d spacing type of zeolite nu-1.

EXAMPLE 15 Synthesis at higher temperature

Example 7 was repeated with the modification that the mixture wasreacted at 250° C for 24 hours. The product was nu-1 of the high dspacing type similar to that of Example 14.

EXAMPLE 16 Synthesis with and without seed

Three synthesis runs were carried out using a reaction mixture havingthe molar composition

    5.4 Na.sub.2 O . 5.6 Q.sub.2 O . Al.sub.2 O.sub.3 . 55.6 SiO.sub.2 . 3327 H.sub.2 O

in each run sodium aluminate (2.4 g) sodium hydroxide (3.8 g) and TMAOH(54 g of solution) were dissolved in 300 g water and the resultingsolution was stirred into a suspension of silica KS 300 (45 g) in 458 gwater.

(a) To one mixture were added 4.5 g of zeolite nu-1 of the low d spacingtype made in Example 10 above. The resulting seeded mixture was heatedat 180° C for 24 hours. The solid phase was collected on a filter,washed and dried. Its X-ray diffraction pattern was substantially thesame as that of the product of Example 14, that is, a high d spacingsplit peak variant of zeolite nu-1.

(b) The second mixture was heated at 180° C without any addition of seedzeolite. Conversion to zeolite nu-1 took 72 hours. Its X-ray diffractionpattern was substantially the same as that of the product of Example 14,that is, a split peak variant of zeolite nu-1.

(c) The third mixture was seeded with 2.5 g of zeolite nu-1 of the splitpeak type produced in Example 13. Its X-ray diffraction pattern was thesame as that of the seed zeolite.

EXAMPLE 17 Zeolite nu-1 with higher silica to alumina ratio

a synthesis mixture of composition

    3.74 Na.sub.2 O . 17 Q.sub.2 O . Al.sub.2 O.sub.3 . 120 SiO.sub.2 . 3527 H.sub.2 O

was made up be dissolving sodium aluminate (1.8 g), sodium hydroxide (2g) TMAOH (124 g of solution) in 200 g water and stirring the resultingsolution into a suspension of silica KS 300 (72 g) in 340 g water. Themixture was reacted in a 1 liter "Pyrex" (R.T.M.)-lined in a 5 literrocking autoclave under 20 ata nitrogen pressure at 170° C for 3 days.The solid phase was collected on a filter, washed and dried. It had thecomposition

    0.1 Na.sub.2 O . 2.2 Q.sub.2 O . Al.sub.2 O.sub.3 120 SiO.sub.2 . 4.3 H.sub.2 O

its X-ray diffraction pattern was substantially the same as that of theproduct of Example 12, that is, the multiple-peak variant of zeolitenu-1.

EXAMPLE 18

The reaction mixture was as shown in Table 9. The sodium hydroxide wasdissolved in the mixture of TMAOH solution and water. The silica andmetakaolin were dispersed in the resulting mixture with vigorousstirring. The slurry was then reacted quiescently for 8 days at 180° Cin a "Pyrex" (R.T.M.)-lined autoclave in the presence of gaseousnitrogen at 20 ata pressure, then let-down and cooled to almost 60° C.The solid phase was collected on a filter, washed with 1 liter of hotwater, dried for 17 hours at 80° C and examined for chemical compositionand by X-ray diffraction. Its composition was

    0.7 Na.sub.2 O . 2.1 Q.sub.2 O . Al.sub.2 O.sub.3 . 55 SiO.sub.2 . 7 H.sub.2 O

and its X-ray diffraction pattern was substantially the same as that oflow d spacing type nu-1 zeolite.

                                      TABLE 9                                     __________________________________________________________________________                 Molar Contribution                                               Ingredient   Al.sub.2 O.sub.3                                                                    SiO.sub.2                                                                           Na.sub.2 O                                                                          Q.sup.+                                                                             OH.sup.-                                                                            H.sub.2 O                          __________________________________________________________________________    Silica KS 300 18 g 0.294 0.0032      0.0064                                   TMAOH 19.6 g                   0.0538                                                                              0.0538                                                                              0.816                              Water 306 g                                17.0                               Metakaolin 1.1 g                                                                           0.005 0.01                                                       Sodium hydroxide 4.8 g   0.06        0.12                                                  0.005 0.304 0.0632                                                                              0.0583                                                                              0.1802                                                                              17.816                             per Al.sub.2 O.sub.3                                                                       1.0   60.8  12.64 10.76 36.04 3563.2                             __________________________________________________________________________

EXAMPLE 19

The reaction mixture was as shown in Table 10. The procedure was thesame as in Example 18, except that the reaction time was 3 days and thereaction was carried out in a rocking autoclave with glass lining.During the reaction the silica/alumina beads broke down giving a finelydivided solid phase. The product zeolite had the composition

    0.3 Na.sub.2 O . 1.9 Q.sub.2 O . Al.sub.2 O.sub.3 . 52 SiO.sub.2 . 10 H.sub.2 O

and its X-ray diffraction pattern was substantially the same as that ofthe low d spacing type of nu-1 zeolite.

                                      TABLE 10                                    __________________________________________________________________________                 Molar Contributon                                                Ingredient   Al.sub.2 O.sub.3                                                                   SiO.sub.2                                                                         Na.sub.2 O                                                                        Q.sup.+                                                                            OH.sup.-                                                                           H.sub.2 O                                 __________________________________________________________________________    Silica sol 459 g  2.3               17.85                                     Sodium hydroxide 36.7g                                                                              0.46      0.92                                          TMA 25% w/w aq. 180.6g    0.496                                                                              0.496                                                                               7.53                                     Silica/alumina                                                                  32.3g      0.046                                                                              0.46                                                        cracking catalyst                                                             (1 mm beads)                                                                  Water 60.8 g                         3.67                                                  0.046                                                                              2.76                                                                              0.46                                                                              0.496                                                                              1.416                                                                              29.05                                      per Al.sub.2 O.sub.3                                                                      1.0  60  10  10.8 30.78                                                                              631.5                                     __________________________________________________________________________

EXAMPLE 20

The reaction mixture was as shown in Table 11. The time was 2 days, arocking autoclave was used and its lining was made of "Pyrex" (R.T.M.)The solid phase resulting from this reaction was in bead form.Incomplete formation of zeolite nu-1 had taken place as a result of thelow silica content and alkalinity of the reaction mixture and shortreaction time. The zeolite product had the chemical composition

    0.9 Na.sub.2 O . 1.5 Q.sub.2 O . Al.sub.2 O.sub.3 . 40 SiO.sub.2 . 15 H.sub.2 O

and an X-ray diffraction pattern characteristic of zeolite nu-1.

                                      TABLE 11                                    __________________________________________________________________________                Molar Contribution                                                Ingredient                                                                                Al.sub.2 O.sub.3                                                                   SiO.sub.2                                                                         Na.sub.2 O                                                                         Q.sup.+                                                                           OH.sup.-                                                                          H.sub.2 O                                   __________________________________________________________________________    Waterglass 59.3 g                                                                              0.27                                                                              0.135    0.27                                                                              1.93                                        TMAOH solution 59 g       0.16                                                                              0.16                                                                              2.46                                        Silica/alumina                                                                            0.054                                                                              0.54                                                           37.9g                                                                       cracking catalyst                                                             Water 575 g                       31.9                                                    0.054                                                                              0.81                                                                              0.135                                                                              0.16                                                                              0.43                                                                              36.29                                        per Al.sub.2 O.sub.3                                                                     1.0  15  2.5  2.96                                                                              7.96                                                                              672                                         __________________________________________________________________________

EXAMPLE 21 Dye adsorption properties

The dye adsorption properties of zeolite nu-1 in two forms, A-hydrogenform containing TMA and B-hydrogen form without TMA, were compared withthose of zeolites Y, ZSM 5 and mordenite, each in hydrogen form, byadding 0.2 g of the zeolite to 5 ml of a saturated aqueous solution ofthe dye, shaking for 5 minutes, allowing to stand overnight, filtering,washing thoroughly and observing the extent of coloration of thezeolite. The adsorption of dyes containing cation groups is shown inTable 12.

                                      TABLE 12                                    __________________________________________________________________________           DYE                                                                                  Carbo- Methyl Pheno- Toluylene                                  Zeolite                                                                              Acriflavine                                                                          cyanine                                                                              Red    Safranine                                                                            Red                                        __________________________________________________________________________    nu-1(TMA)                                                                            nil    very strong:                                                                         very strong                                                                          NA     NA                                                       purple                                                          nu-1   nil    very strong:                                                                         very strong                                                                          nil    nil                                        (no TMA)      purple/blue                                                     Y      medium nil    nil    nil    nil                                        ZSM 5  very strong                                                                          very strong:                                                                         very strong                                                                          very strong                                                                          very strong                                              blue                                                            mordenite                                                                            very strong                                                                          very strong:                                                                         nil    nil    nil                                                      blue                                                            __________________________________________________________________________

The adsorption of dyes not containing cation groups is shown in Table13.

                  TABLE 13                                                        ______________________________________                                                 DYE                                                                                                   Aluminon                                     Zeolite    Alizarin   Aurin      C.I. 724                                     ______________________________________                                        nu-1 (TMA) very strong                                                                              nil        NA                                           nu-1 (no TMA)                                                                            very strong                                                                              medium     nil                                          Y          nil        nil        nil                                          ZSM 5      nil        very strong                                                                              very strong                                  mordenite  weak       medium     very strong                                  ______________________________________                                    

We claim:
 1. A process for the isomerisation of alkyl benzenes whichcomprises contacting a feed of an alkyl benzene or a mixture of alkylbenzenes under isomerisation conditions in the liquid or vapour phasewith a catalyst comprising zeolite nu-1 having a composition expressedby the formula

    0.9 to 1.3 R.sub.2 O . Al.sub.2 O.sub.3 . 20 to 150 SiO.sub.2 . 0 to 40 H.sub.2 O

where R is one or more of hydrogen, ammonium, phosphonium or 1/n of acation having a valency n and having a X-ray diffraction pattern when Ris H substantially as shown in Table
 1. 2. A process according to claim1 in which the reactants are present in the vapour phase, added freehydrogen is substantially absent, the temperature is in the range200°-450° C, the pressure in the range 1 to 5 ata and the catalystcontains substantially no hydrogenation/dehydrogenation components.
 3. Aprocess according to claim 2 in which the starting materials includexylenes and ethylbenzene and the process conditions are chosen so thatethylbenzene is converted.